Mass spectrometers are used for producing mass spectrum of a sample to find its composition. This is normally achieved by ionizing the sample and separating ions of differing masses and recording their relative abundance by measuring intensities of ion flux. For example, with time-of-flight mass spectrometers, ions are pulsed to travel a predetermined flight path. The ions are then subsequently recorded by a detector. The amount of time that the ions take to reach the detector, the “time-of-flight”, may be used to calculate the ion's mass to charge ratio, m/z.
Additional information (aside from precursor mass) on a given ion can then be obtained by fragmenting the ion via CID (collision induced dissociation) in a collision cell (or other mean) generate an MSMS spectrum. In most instrument with MSMS capabilities, the process of generating a mass spectrum, selecting an precursor ion and performing an MSMS (mass spectrum/mass spectrum) spectrum can be performed in an automated mode over and LC (liquid chromatography) analysis (or by infusion). This mode of acquisition is frequently referred to as Information Dependant Acquisition (IDA) or Data Dependant Experiment (DDE).
Often, samples to be analyzed include bodily fluids taken from test subjects such as animals in laboratories. As a result, the sample ions typically include both drug metabolites of interest, as well as irrelevant endogenous ions from the test subject. If the drug metabolites of interest are in low concentrations, creating a total ion chromatogram (TIC) of the sample ions may result in difficulties in identifying the drug metabolites. The ion flux or drug metabolites with low concentrations may be subsumed within the flux signals of the irrelevant endogenous ions.
The applicants have accordingly recognized a need for systems and methods for analyzing and identifying ions from samples.